Retrofitting Soft-Story Buildings

Most California homes and buildings will need earthquake retrofitting to prevent damage or complete failure during seismic activity.

The City of Los Angeles currently considers the following structures the most vulnerable during a quake:

A wood frame building with 2 or more stories

Any structure built before January 1, 1978, when new building codes were adopted

A building with a lower level parking garage or comparable open floor space (soft-story).

A soft-story building is a multi-story structure with a weak first floor. The weakness is caused by large windows and doors around the perimeter of the floor, and/or big, open spaces inside. A common type of soft-story structure is an apartment building or retail business constructed on top of a parking garage. Other types of soft-story structures include office buildings with large 1st floor lobbies and ground-floor retail stores with wide windows and entrances.

Damage reports from several recent earthquakes noted that, in many cases, almost half the buildings that collapsed or were severely damaged during the quake were soft-story.

The primary reason for soft-story failure is the building’s inability to withstand the side-to-side push that can come from an earthquake. Once the weaker first floor destabilizes, the remaining floors will start to collapse.

In the Los Angeles area alone, there are tens of thousands of soft-story structures. All of these building will need retrofitting to prevent failure when the ground starts to shake.

The purpose of retrofitting for earthquakes is to simply strengthen the structure so it can withstand lateral movement. The process begins with a foundation inspection to determine what kind of retrofitting is needed. Shear walls, steel frames and plywood can be added for extra support.

We’ve done many soft story retrofits in Los Angeles and California to minimize damage and personal injury during an earthquake. If you own a soft-story structure that hasn’t been retrofitted, we’ll inspect your property and come up with a plan to make it earthquake ready.